Avalanche Forecast

Issued: Dec 25th, 2012 3:00PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Deep Persistent Slabs.

pgoddard, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain on Thursday

Weather Forecast

Wednesday: Light SW winds. Strong arctic outflow winds in the valleys. Alpine temp -8. A few cm snow.Thursday: Light SW winds. Alpine temp -7. Moderate snow.Friday: Moderate to strong SW winds. Alpine temp around -6. Moderate snow.

Avalanche Summary

Several natural size 1-2 loose dry and thin slab avalanches failed in terrain features wind-loaded by outflow (down-valley) winds over the past few days. Explosives triggered size 2-3 slabs which failed near the ground in facets last weekend.

Snowpack Summary

Wind slabs and cornices have developed on a fairly widespread basis and may be found on many slopes due to variable wind directions. Surface faceting is likely to continue while the weather remains cold. A layer of surface hoar buried in the upper metre of the pack has been observed in the Shames backcountry. The mid-pack is generally well settled. Near the base of the snowpack, a crust/facet layer continues to give hard, sudden results in snowpack tests. This weakness is unlikely to be triggered by a single person, but it remains possible with a very heavy load (e.g. cornice fall) or from a thin-spot trigger point.

Problems

Wind Slabs

Wind slabs have formed in response to down-valley winds. These could be triggered by the weight of a person or snowmobile.

Be aware of the potential for wide propagations due to the presence of hard windslabs.>Stay well to the windward side of corniced ridges.>Use ridges or ribs to avoid pockets of wind loaded snow.>

Aspects: North, North East, East, South East, South, South West.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Deep Persistent Slabs

A deeply buried weakness may be triggered from thin, rocky snowpack areas or with a large trigger.

Choose the deepest and strongest snowpack areas on your run.>Be aware of thin areas that may propagate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 7

Valid until: Dec 26th, 2012 2:00PM